Rename rrd-files when changing target name in Cricket

The target names in the Cricket configuration defines the name of the rrd-file where collected data is stored. If the target name changes, a new file is created. This makes the historical data unavailable. It is possible to avoid this by using the rrd database when creating the target to see if the target name has changed. This is to be added to makecricketconfig, so that any changes in the target names are detected and the corresponding rrd file is renamed to match the new target name.